Electrothermal switch.



No. 831,847. PATENTED SEPT. 25, 1906.

J. ERIOKSON. ELEOTROTHERMAL SWITCH.

APPLICATION FILED DEC. 31, 1904.

(027722 Jaisf fill 6 721 021 'UNITED STATES PATENT OFFICE.

JOHN ERICKSON, ELECTRIC COMPANY,

ELECTROTHERMAL SWITCH.

Specification of Letters Patent.

Patented Sept. 25, 1906.

Application filed December 31. 1904- Serial No. 239,131.

To all whom it may concern: v

Be it known that I, JOHN ERICKSON, a citizen of the United States of America, and a resident of Chicago, Cook county, Illinois, have invented a certain new and useful Imrovement in Electrothermal Switches, of which the following is a specification.

My invention relates to switches of that particular character in which the circuit-controlling contacts are opened or closed as a result of the heat generated by the assage of current, either of abnormal strengtli or for an abnormal period of time, through a suitable resistance. Y

Generally stated, the object ofmy invention is the provision of an improved, simplified, and highlyeflicient electrothermal switch of the foregoin general character.

A special object is t e provision of an improved construction and arrangement by which the switchafter it has been operated by an abnormal current-flow may be restored to its normal condition without the necessity of repairing or renewing any of its parts.

Another object is thepro vision of an imroved construction and arrangement wherey the switch-contacts are operated by the expansion of a suitable substance-such, for example, as hard rubber or rubber vulcanite- "and as a result of the heat generated'by the resistance.

A further object is to so construct the switch that a comparatively wide break or separation of .the normally closed switchcontacts may be accomplished as a result of only a comparatively slight expansion on'the part. of the thermal member or expansible substance.

It is also an object of course to provide such details and features of improvement as will tend to increase the general efficiency and serviceability of a device. of this particular character.

In'the accompanying drawings, Figure 1 is a side elevation ofan electrothermal switch embodying the principles of my invention,

A the said switch being shownv in its normal condition and a 1 heat-coil being shown removed for conven-.

portion of the winding or ience of illustration. Fig. 2 is a view similar to Fig. ,1, but showing the normally closed switch-contacts in their "operative or separated condition. Fig. 3 is a perspective of the end portion of one of; the switch-contacts.

switch comprises a suitable base A,

Upon the said v 13 andCcan supports Fig. 4 is a vertical and longitudinal section of the switch shown in the preceding figures.

As thus illustrated, my improved electrothermal switch may be employed in various connections-such, for example, as maintaining the continuity of a circuit until such time as the presence of a trespassing or abnormal current-flow in the circuit shall endanger the apparatus included in said circuit.

As shown, my improved electrothermal preferably of insulating material. basetwo metal springs or flexible supports B and C are mounted and arranged a suitable distance apart. The flexible support B has its upper endportion extended to provide a horizontal or substantially horizontally disposed spring 1), and the free end portion of this flexible or spring-like member I) is preferably provided with a small roller b, as shown more clearly in Fig. 3. Preferably the upper end portion of the flexible support C is extended to provide a stop or abutment c, againstwhich the roller b may bear, and which thus serves as one of the normally closed switch-contacts. It will be observed that the upper portions of the two flexible supports B and C are preferably rigidly connected or separated by means of a horizontally-disposed thermal member D. The said thermal member may be of any suitable heat responsive or expansible substanceas, for example, It made of such material, the said thermal member preferably has its ends provided with metal caps d. The flexible metallic s'u ports be provided with slots'a apted to receive screws (1, which latter extend through the said supports and engage thread-v ed openings inthe ends of the caps d. In this way the opposite ends of the said thermal member are connected with the two flexible B and C in such manner as to permit of more or less adjustment and a consequent accurate positioning of the different parts of the switch. Upon the said thermal member a coil of insulated wire E is mounted. -As shown, one terminal of said 0011 is connected with the ca d, which is in contact with the support B, w ile the other terminal hard rubber or rubber vulcanite.

IOO

is left free or connectediwith some suitable binding-post on the base. a V a The spring-support Cis providediwithi'a cause thethermal member D to expand end This will' obviously cause moreor less Wise.

[ separation of the spring-supports B and C I that is to say, these two supports will bend or flex away from each other as a result of the endwise expansion of the said thermal member. Normally the spring I) is preferably under tension while the contacts are 'closed,'and it is evident, therefore, that said rin 'b will fly upward as soon as the springs an Qmove apart sufliciently to'drawthe, roller 11 out from under the stop or abutment 2o 0. In. this way only a comparatively sli ht expansion on the" part of the thermal mem er 'D is. sufficient. to produce theacfii'nparatively wide gap between the separated contacts. hen thecoiland the thermal member are a 2 5 allowed to cool upon the cessation of current through the coil as soon'as the contacts separate, the thermal member D then contracts and allows thesprin -support s B and) to return to their normal posltions. After this 0- the spring I) can then be pressed downward until the roller 6 is again can htand'held by the under side of the stop oi hutment c.

It will be understood, of course,'that the coil E may consist of any suitable amount of 3 5 wire wound upon more or less of the thermal member D. Also it is obvious-that any other suitable resistance ma be associated with the said thermal member-that'is to say, any form of resistance whichwill be cao pable' of generating the heat necessary for expanding the said. thermal member. Again, it is evident that the switch-contacts ma be of any suitable or desired number-and 0 ar 'acter and may be connectedv and'op'erated 7 5" by the thermal member in any suita e or r e. quired manner. 1 J Obviously my improved switch when-'0 erated can .berestored to its iinormal 00. 'tion without the necessity of repairingorre- 5o newing any-of its various parts or .'essential elements. he]. thermal 'portion i-of lithe switch. is self-restoring, so tbjfspeak, inas- ".much as it is'capable of restoring itselfto its 'normal condition, and it willbefseenthat the 5 5 said restoration .is

V: i v thii 'spring-supports B and'C'are tension} tonornia'lIy subject" the 1 rate restoration of hard rubber or rubber 4. of. suchj-chanacter';that everything in the switch, with, the one exceplcr originali p'osi-:

. thermal member D to a pull or tensile strain,

although this is not a solutely necessary. This is preferably accomplished b so con-- structing and tensioning the arm that its u -pull tends constantly to crowd or force 70 t e supports B and C'apart; but when the. arm I) is released the thermal member D'isl then subject to an endwise compressive strain by the ressure toward each other of the. supports all parts to their normal condition.

. The upper end of thespring C is preferably beveled, was shown, or "provlded with some other e uivalent means for engaging the So roller 6 and for facilitating the restoration of the roller to circuit-closing position. 4

I do not, of course, limit myself to the exact construction shown and described, as the. construction can be varied or changed and 85- still retain the novel features and combinations and advantages of my invention.

What I claim as my inventiolilir 1. An electrothermal switch-,"'qomprising two flexible metallic supports, the end of one o support being-extended to provide a stop or abutment, and the end of the ot' er sup ort. being extended to provide a spring-arm aving its end normally in engagement with said. s'topor abutment, the said spring-armbeing 95 thereby normally under tension, a length of vulcanite disposed horizontallybetw'een the said supports,- the; said length of hard rubber or rubber vulcaniteconstitutingl'a thermal member and hav- 0 ing its ends secured toisaid flexible sulpports, the said thermal member normallysu ject to a tensile strain, but subject to an endwisei compressive strain when the switch is operated, and a suitable resistance associated with, 1'05 said thermal member and connected in series I with said s ring-arm andstop or abutment, whereby tlie circuit .of the resistance is/ opened when the thermal member expands, and thereby-causes the ment. I a V 2; An electrothermal witch comprising two flexible metallic 'su ports, theend of one" support being extende to-provide a switch-i 1'15 contact, and the endof the other supportbe- 'ing extended to provide a spring-arm having its endprovided with aholler, said roller 'normally engaging said switch contact, I and Y thereby constituting asecond switch-contact, ,1 the two contacts being normally closed, .afl-

-length of insulatingmaterial disposed horizontally between the two supports and provided with end caps which are secured to the said supports, the said insulation thereby I I constitutmg a thermal member foro crating r saidcontacts, the saidthermal mm er normally-subject to "a tensile strain, but subject to an endwisehompressi've strain'when the switch is operated, and a su'itableresistance mo.

and C, so asto insure accusaid spr1ng-arm,. to 1 1 10 disengage itself from the said stop or abutassociated with said thermal member and connected in series with said normally closed contacts, whereby the said contacts are dis engaged from each other, and the circuit of said resistance is opened when the two flexible supports are pushed away from each 3. The combination of switch-contacts, a

thermal member connected to operate. said contacts, and a suitable resistance associated with said thermal member, said contacts in; cluding a metal-roller circuitcontrolling contact normally in circuit with said resistance, and a beveled contact in the same circuit and normally engaged by said roller.

4. An electrothermal switch comprising switch-contacts, a thermal member for operating said contacts, said thermal member consisting of an endwise-expansible piece of insulating material, and a suitable resistance associated with said thermal member, said contacts including a metal-roller circuit-controlling contact normall in circuit with said resistance, and a bevele contact in the same circuit and normally e aged b said roller.

5. An electrothermal switcii comprising switch-contacts, a thermal member for oper-.

ating said contacts, said thermal member consisting of a rod of hard rubber or rubber vulcanite, the said thermal member nor-' mally subject to a tensile strain, but subject to an endwise-compressive strain when the switch is operated, and a suitable resistance wound upon said thermal member, said contacts including a metal-roller circuit-controlling contact normall in circuit with said resistance, and a bevele contact'in the same circuit and normally en aged b said roller. 6. .An electrotherma switcli com risin normally closed switch-contacts, a t erma member, and a suitable resistance associated with said thermal member and connected in series with said normally closed contacts, .the said thermal member normally subject to a tensile strain, but subject to an endwise-compressive strain when the switch is operated,

whereby the circuit of said resistance is broken when the contacts are separated by the expansion of said thermal member in response to the heat generated by said resistance, said contacts including a metal-roller circuit-controlling contact normally in circuit with said resistance, and a beveled contact in the same circuit and normally engaged by said roller.

7. An electrothermal switch com rising two flexible supports connected by a ength of insulating material, said insulating material being expansible when subjected to heat, and thereby constituting a thermal member, the said thermal member normally subject to a tensile strain, but subject to an endwiSe-compressive strain when the switch is operated, normally closed contacts adapt ed to be se arated, when said supports are bent away om each other, by the expansion of said thermal member, and a suitable resistance wound upon said thermal member and connected in series with' said normally closed contacts, said contacts including a metal-roller circuit-controlling contact normally in circuit with. said resistance, and also including a beveled contact in the same circuit and normally engaged by said roller.

8. An electrothermal switch comprising switch-contacts, an expans'ible body of insulating material for operating said contacts,

and a suitable resistance associated with said 'insulat' material, said contacts including a metal-rol er I circuit-controlling contact normall in circuit with said resistance, and a beve ed contact in the same circuit and normally engaged by said roller.

9. The combination of a metal-roller circuit-controlling contact, a hea generating resistance normally in circuit wit said roller,

a beveled contact in the same circuit and normally engaged by said roller, and a thermal means for operating said contacts, substantially as and for the purpose set forth:

Signed by me at Chicago, Cook county, Illinois, this 1st .day of December,1904.

' JOHN ERICKSON.

Witnesses: v

W. LEE CAMPBELL, R'. G. Grr'ronn. 

